The present invention is generally directed to toner processes, and more specifically to microsuspension processes for the preparation of toner compositions. In embodiments the present invention is directed to the economical preparation of toners without the utilization of the known pulverization and/or classification methods, and wherein toners with an average volume diameter of from about 3 to about 21 microns can be obtained. The resulting toners can be selected for known electrophotographic imaging and printing processes, including color processes, and lithography. In embodiments, the present invention is directed to a process comprised of homogenizing microsuspended particles of from about 0.05 micron to about 2 microns in volume diameter, containing a resin and pigment in an aqueous solution containing surfactant, followed by aggregating the aforementioned pigmented particles by heating to generate toners with an average particle volume diameter of from about 3 to about 21 microns. In another embodiment thereof, the present invention is directed to an in situ process comprised of dissolving a polymer resin such as a polyester, polyacrylate, styrene butadiene, or polymethacrylate of from about 5 to about 80 weight percent, and a pigment such as HELIOGEN BLUE.TM. or HOSTAPERM PINK.TM. of from about 1 to about 10 weight percent in an organic solvent such as methylene chloride or ethyl acetate; dispersing the resulting mixture in an aqueous solution containing surfactants such as sodium dodecylsulfate and polyoxyethylene nonyl phenyl ether, thereby obtaining suspended particles of from about 0.05 micron to about 2 microns in volume diameter; removing the organic solvent by stirring and optionally by heating from about 25.degree. C. to about 60.degree. C.; homogenizing the mixture at about 500 to about 4,000 revolution per minute; and followed by aggregating the aforementioned pigmented particles by heating to generate toners with an average particle diameter of from about 3 to about 7 microns. In an embodiment, the present invention is directed to a process comprised of homogenizing microsuspended particles of from about 0.05 micron to about 2 microns in volume diameter, containing a resin and pigment, in an aqueous solution containing surfactant, followed by aggregating the aforementioned pigmented particles by heating to generate toners with an average particle volume diameter of from about 3 to about 7 microns. In another embodiment thereof, the present invention is directed at a process comprised of dissolving a polymer resin, such as a polyester, polyacrylate or polymethacrylate of from about 5 to about 80 weight percent in an organic solvent such as methylene chloride or ethyl acetate; dispersing the resulting mixture in an aqueous solution containing surfactants such as sodium dodecylsulfate and polyoxyethylene nonyl phenyl ether, thereby obtaining suspended particles of from about 0.05 micron to about 2 microns in volume diameter; removing the organic solvent by stirring and optionally by heating from about 25.degree. C. to about 60.degree. C.; adding a pigment, such as HELIOGEN BLUE.TM. or HOSTAPERM PINK.TM., of from about 1 to about 10 weight percent and homogenizing the mixture at about 500 to about 4,000 revolutions per minute; followed by aggregating the aforementioned pigment and suspended particles by heating to generate toners with an average particle diameter of from about 3 to about 7 microns. The aforementioned toners are especially useful for the development of colored images with excellent line and solid resolution, and wherein substantially no background deposits are present.
In color reprography, especially process color reprography wherein pictorial images are generated, high gloss of from about 50 gloss units to about 80 gloss units as measured by the Gardner Gloss meter is highly desirable. Additionally, toners which fix onto paper at low fusing temperatures, such as from about 125.degree. C. to about 150.degree. C., are desirable to prolong the lifetime of the fuser and reduce its energy consumption. Accordingly, in order to satisfy the aforementioned high gloss and low fusing temperature requirements, it is advantageous to utilize conventional toners comprised of polyesters as the resin binder. However, the process for obtaining conventional toners and toners in generally usually require the utilization of pulverization and cumbersome classification methods which are expensive, especially wherein small size toners of from about 3 microns to about 7 microns are desired. The process of this invention is directed to the economical preparation of toners containing, for example, polyester resins without the utilization of the known pulverization and attrition methods and wherein toners with an average volume diameter of from about 3 to about 7 microns can be obtained. Additionally, with the toners of this invention, high gloss of from about 50 to about 80 gloss units as measured by the Gardner gloss meter, and low fixing temperature of from about 125.degree. C. to about 150.degree. C. are attained in embodiments.
There is illustrated in U.S. Pat. No. 4,996,127 a toner of associated particles of secondary particles comprising primary particles of a polymer having acidic or basic polar groups and a coloring agent. The polymers selected for the toners of this '127 patent can be prepared by an emulsion polymerization method, see for example columns 4 and 5 of this patent. In column 7 of this '127 patent, it is indicated that the toner can be prepared by mixing the required amount of coloring agent and optional charge additive with an emulsion of the polymer having an acidic or basic polar group obtained by emulsion polymerization. Additionally, this process involves the preparation of emulsion addition type resins, such as that obtained from styrene, ethyl acrylate and the like, and wherein it is believed that polyesters cannot be effectively obtained. Additionally, note column of '127 patent wherein the pigment is added with the emulsion particle. Also, note column 9, lines 50 to 55, wherein a polar monomer such as acrylic acid in the emulsion resin is necessary, and toner preparation is not obtained without the use, for example, of acrylic acid polar group, see Comparative Example I. The process of the present invention does not utilize polar acid groups, and toners can be prepared with polyester resins without containing polar acid groups. In U.S. Pat. No. 4,983,488, a process for the preparation of toners by the polymerization of a polymerizable monomer dispersed by emulsification in the presence of a colorant and/or a magnetic powder to prepare a principal resin component and then effecting coagulation of the resulting polymerization liquid in such a manner that the particles in the liquid after coagulation have diameters suitable for a toner. It is indicated in column 9 of this patent that coagulated particles of 1 to 100, and particularly 3 to 70, are obtained. This process is thus directed to emulsion type resins and monomers therefrom, and coagulants must be utilized. With the process of the present invention, addition type resins and polyester resins utilized for pictorial or process color applications with low fusing temperatures and high gloss can be obtained. Similarly, the aforementioned disadvantages are noted in other prior art, such as U.S. Pat. No. 4,797,339, wherein there is disclosed a process for the preparation of toners by resin emulsion polymerization and spray drying; and U.S. Pat. No. 4,558,108, wherein there is disclosed a process for the preparation of a copolymer of styrene and butadiene by specific suspension polymerization. More specifically, this patent discloses a microsuspension polymer process wherein a resin, preferably a polyester and solvent, is microsuspended to from about 0.05 to about 1 micron in volume diameter followed by aggregating to toner size particles of from about 3 microns to about 7 microns in volume diameter as measured by the Coulter Counter, and exhibit low fixing temperature of from about 125.degree. to about 150.degree. C., and high gloss of from about 50 to about 80 gloss units as measured by the Gardner Gloss device.